The most abundant antioxidants in hazelnuts are known as phenolic compounds. They are proven to help decrease blood cholesterol and inflammation. They could also be beneficial for heart health and protecting against cancer (, , ).

An 8-week study showed that eating hazelnuts, with or without the skin, significantly decreased oxidative stress compared to not eating hazelnuts, which caused no effects ().

The majority of the antioxidants present are concentrated in the skin of the nut. However, this antioxidant content could decrease after the roasting process (, , ).

Therefore, it is recommended to consume whole, unroasted kernels with the skin rather than peeled kernels, either roasted or unroasted ().

Summary Hazelnuts are rich in phenolic compounds that have been shown to increase antioxidant protection in the body. It is best to eat hazelnuts whole and unroasted to ensure you get the highest concentration of antioxidants.

In hazelnuts, the high concentration of antioxidants and healthy fats may increase antioxidant potential and lower cholesterol levels in the blood (, ).

One month-long study observed 21 people with high cholesterol levels who consumed 18–20% of their total daily calorie intake from hazelnuts. The results showed that cholesterol, triglycerides and bad LDL cholesterol levels were reduced ().

Participants also experienced improvements to artery health and inflammation markers in the blood.

Moreover, a review of nine studies including over 400 people also saw reductions in bad LDL and total cholesterol levels in those who ate hazelnuts, while good HDL cholesterol and triglycerides remained unchanged ().

Hazelnuts’ high concentration of antioxidant compounds, vitamins and minerals could give them some anti-cancer properties.

Among other nuts like pecans and pistachios, hazelnuts have the highest concentration of a category of antioxidant known as proanthocyanidins ().

Some test-tube and animal studies have shown that proanthocyanidins may help prevent and treat some types of cancers. It is thought that they protect against oxidative stress and enzyme regulation properties (, ).

Additionally, hazelnuts are rich in vitamin E, another powerful antioxidant that has exhibited possible protection against cell damage that could cause or promote cancer ().

Similarly, hazelnuts provide a whopping 87% the RDI for manganese in a one-ounce serving ().

Manganese has shown to help the functions of specific enzymes that could reduce oxidative damage and decrease the risk of cancer (, ).

A couple of test-tube studies showed that hazelnut extract could be beneficial in the treatment of cervical, liver, breast and colon cancer (, ).

Furthermore, an animal study using a product made from hazelnut skin extract resulted in a decreased risk of colon cancer after the eight-week study period ().

Since most studies investigating the benefits of hazelnuts against cancer development have been done in test tubes and animals, more studies are needed in humans.

Summary The high concentration of antioxidant compounds, vitamin E and manganese in hazelnuts may help decrease the risk of certain cancers, though more research is needed.

Hazelnuts have been linked to reduced inflammatory markers, thanks to their high concentrations of healthy fats.

One study investigated how eating hazelnuts affected inflammatory markers, such as high-sensitivity C-reactive protein, in 21 people with high cholesterol levels.

The participants experienced significant reductions in inflammation after four weeks of following a diet in which hazelnuts accounted for 18–20% of their total calorie intake ().

Moreover, eating 60 grams of hazelnuts every day for 12 weeks helped reduce inflammatory markers in overweight and obese people ().

Another study examined how eating hazelnuts affected inflammation. It showed that eating 40 grams of hazelnuts may reduce the inflammatory response in healthy people ().

Similarly, 50 people with metabolic syndrome experienced a decrease in inflammation after consuming 30 grams of a combination of raw nuts — 15 grams walnuts, 7.5 grams almonds and 7.5 grams hazelnuts — for 12 weeks, compared to a control group ().

However, most studies conclude that eating hazelnuts alone is not enough. In order to reduce inflammation, it is also important to follow a calorie-controlled diet ().

Summary Hazelnuts may help prevent and decrease inflammation due to their high concentrations of healthy fats. Nevertheless, other factors are also important.

Hazelnuts can be incorporated into the diet as a healthy snack or as an ingredient in many dishes.

You can purchase and enjoy them raw, roasted, whole, sliced or ground. Interestingly enough, it seems that people prefer sliced and whole hazelnuts rather than ground ones ().

While the highest concentration of antioxidants is in the skin, some recipes require you to remove the skin. This can be done by baking the kernels in the oven for about 10 minutes, which makes the skins easy to then peel.

Peeled hazelnuts can be ground to make flour for baking or to make hazelnut butter, a nutritious spread.

Moreover, hazelnuts can also be coated with chocolate or spices, like cinnamon or cayenne, for a sweet or spicy treat.

They also make a great complement to cakes or topping for ice creams and other desserts.

Summary Hazelnuts can be found whole, sliced, ground, raw or roasted. They are commonly eaten as a snack or added to baked goods and other dishes. It’s best to eat them with the skin on.